The present invention relates to thermal sensing devices. More particularly, the present invention relates to thermal sensing devices for use with an integrated circuit such as a microprocessor.
Integrated circuits (ICs) generate heat when powered by an electric source such as a power supply. ICs are generally susceptible to overheating which may cause the IC or the device in which the IC is employed to fail, to malfunction, to be uncomfortable for the user to handle, or otherwise diminish the utility of the IC or the device. Particularly, the overheating of ICs is becoming a more serious problem as more powerful and more complex ICs are packaged in smaller and lighter IC packages. For example, powerful microprocessors which are utilized in compact laptop computers and notebook computers, often heat the laptop computer or notebook computer until the laptop computer or notebook computer is uncomfortable to hold. Further, the use of lighter, less expensive, and highly insulative plastic IC packages compounds the overheating problems.
Thus, thermal management of ICs is necessary to prevent the IC and the device in which the IC is employed from overheating. A variety of thermal management devices and techniques have been employed to attempt to prevent ICs from overheating. For example, some ICs are encapsulated in packages that have a fan mounted on the package. The fan forces air onto the package in order to cool the IC. These fans are generally constantly turned ON and consuming power. These fans are disadvantageous because they require space, power and are expensive.
Other thermal management approaches attempt to limit the amount of time that the thermal management device is employed. For example, one approach counts the number of clock cycles supplied to or used by the IC and assumes that the IC is overheated after a particular number of clock cycles. A thermal management device such as a fan, or a thermal management technique or routine such as decreasing the frequency of clock signals is employed after the particular number of clock cycles has elapsed. Counting the number of clock cycles is disadvantageous because the ambient conditions are not considered. Therefore, the thermal management device or technique may be inefficiently utilized when the IC is not overheating or not utilized at all when the IC is overheating. Also, counting the number of clock cycles requires significant additional hardware.
It would therefore be advantageous to have a thermal sensor which could directly sense temperature within or on the outside of the IC. Further, a thermal sensor could advantageously provide a control signal for use by a thermal management device or routine when the temperature within the IC is above a threshold. Thus, a thermal sensor could advantageously employ thermal management devices or techniques only when the temperature within the IC is in fact too high.